>>> from urllib.parse import urlparse # python2: from urlparse import urlparse
>>> urlparse('actually not a url')
ParseResult(scheme='', netloc='', path='actually not a url', params='', query='', fragment='')
>>> urlparse('http://google.com')
ParseResult(scheme='http', netloc='google.com', path='', params='', query='', fragment='')

import urllib.request as req
import urllib.parse as p

def foo():
    url = 'http://bar.com'
    request = req.Request(url)
    try:
        response = req.urlopen(request)
        #response is now a string you can search through containing the page's html
    except:
        #The url wasn't valid

import validators
url = 'YOUR URL'
validators.url(url)